Rapamycin is the most consistent lifespan-extending intervention across multiple animal models, working by inhibiting mTOR, a nutrient-sensing pathway that, when chronically overactive, drives accelerated cellular aging. This robust preclinical data has fueled real off-label human use within longevity medicine circles, almost always using weekly rather than daily pulsed dosing to capture the autophagy benefits while minimizing the immunosuppression that limits its original transplant-rejection use. There is currently no completed long-term human RCT confirming lifespan extension at these doses, and immunosuppression, mouth sores, and altered lipid panels are recognized risks. This is a prescription-only drug requiring physician oversight, baseline labs, and ongoing monitoring — not a self-directed supplement.